Two days ago I noticed my penis head skin was wrinkly. When I get an erection the skin is also like this but when I to make it as big as I can it is normal. I have never had sex but I do masturbate
Are you circumcised? Maybe he's just a bit dry? If it's not causing any troubles for you I would just keep an eye on it and see what happens as the penis (as you would know) often changes during the teen years and has a mind of it's own half the time
I am not a doctor though so if you have any other worrying concerns I would certainly speak to a medical professional about it.